1. Field of the Invention
The present invention relates to a power source control system and power source control method for a portable radio transceiver, and particularly to a power source control system and power source control method for controlling battery voltage in a portable radio transceiver.
2. Description of the Related Art
Power source control systems of the prior art include examples that control battery voltage. One example of such a power source control system is described in Japanese Patent Application Laid-open No. 154118/87. This power source control system includes a back-up device wherein, when the power supply to a device is cut off, a back-up supply current is controlled in accordance with the remaining charge of a secondary battery.
This type of power source control system can extend the life of the battery by detecting the remaining charge of the battery from the discharge rate of the battery, finding the amount of current that can be obtained, and altering the permissible current of the electrical devices connected to the battery.
The power source control system of a portable radio transceiver, moreover, can predict whether the remaining battery charge will last the duration of a particular day in cases in which calls are made on the portable radio transceiver with great frequency based on the amount of call time and the remaining battery charge indicated on the portable radio transceiver, and as a result, allows the user to know when to carry a reserve battery.
There remains the problem, however, that in cases when a user is not making calls on the transceiver with great frequency and therefore does not carry a reserve battery, the user may easily leave the portable radio transceiver in a call waiting state for an extended period of time, only to find that when the user wants to make a call, the battery charge is exhausted and calling is impossible.